1. Field of the Invention
This invention relates to an apparatus for efficiently separating nonmagnetic conductive material such as aluminum or copper from composite input material fed posterior to previous removal of magnetic substance therefrom.
2. Description of the Prior Art
One of the nonmagnetic conductive material separators known heretofore is of the type that is equipped with a rotatable drum having two open ends with its longitudinal center axis inclined, wherein a multiplicity of magnets of mutually opposite polarities are arrayed alternately on the inner surface of the drum with an inclination to the center axis thereof.
The magnets, when rotated in one direction together with the drum, generate a magnetic field rotating in the same direction as that of the drum, and the rotating field thus obtained causes an eddy current in nonmagnetic conductive material contained in the composite input material introduced into the drum through its upper open end. Since the pole boundary lines of the magnets are inclined to the axis of rotation of the drum, the electromagnetic force produced by the eddy current exerts its component on the nonmagnetic conductive material through the inclined drum toward its upper open end. Consequently, according to the above separator, the nonmagnetic conductive material is moved toward the upper open end of the drum against the nonconductive material falling toward the lower open end through the drum due to the weight of gravity, so that the nonmagnetic conductive material can be separated from the input material.
In such a separator, however, the nonmagnetic conductive material and the nonconductive material in the drum are not separated from each other in the circumferential direction of the drum, and the nonmagnetic conductive material is directed toward the upper open end of the drum while being kept in mixture with the nonconductive material. It frequently occurs, therefore, that the nonmagnetic conductive material is accompanied by the nonconductive material to bring about difficulty in achieving positive separation thereof.
In order to enhance the efficiency of separating the nonmagnetic conductive material from the nonconductive material, one method contrivable is to increase the electromagnetic force produced by the eddy current. However, because of the known structure that the magnets for generating a rotating magnetic field are integrated with the drum, it becomes necessary to increase the rotation speed of the drum itself to attain a higher rotation speed of the magnetic field. In this case, when the rotation speed of the drum exceeds a certain value, the separation efficiency is reduced to be extremely low to the contrary by the centrifugal force exerted onto the input material in the drum. Thus, there has been a disadvantage of low separation efficiency in the conventional separators.